The invention relates to a locking mechanism for a bait reel of a belt retractor in a vehicle comprising a carrier coupled to a belt reel of the belt retractor, an inertia mass which is pivoting to a limited extent relative to the carrier and a leaf spring applying the inertia mass in a home position.
The control of a blocking means of a belt reel in a vehicle is effectuated, for example, via a locking mechanism including a carrier coupled to the belt reel which carrier is coupled via a spring to an inertia mass that is pivoting to a limited extent relative to said carrier.
The spring is dimensioned so that the inertia mass co-rotates with the carrier and the belt reel during regular operation of the belt retractor. When the belt reel is accelerated due to sudden webbing extension, for instance by strong deceleration of the vehicle and the resulting displacement of a vehicle occupant, the inertia mass lags behind the movement of rotation of the carrier due to its high mass. By the displacement or swivel of the Inertia mass relative toward the carrier the blocking mechanism of the belt reel is triggered. The latter acts on the belt reel and blocks the same so that further webbing extension is prevented.
Apart from spiral springs, for such locking mechanism frequently a biased leaf spring is used which is clamped al the carrier and/or at the inertia mass. The acceleration at which relative movement of the carrier and the inertia mass takes piece is dependent, apart from the mass of the inertia mass, on the spring bias of said leaf spring. Due to the movement of the inertia mass relative to the carrier the distance and the orientation of the clamping points of the leaf spring are varying, however, so that the spring bias and thus the responsive behavior are varying during the relative movement of the inertia mass and the carrier.
Legal specifications prescribe that the locking mechanism has to be triggered upon acceleration of the webbing extension of from 0.8 to 2 g. These specifications can be easily observed by the locking mechanisms or supports of the spring known so far. However, frequently a substantially narrower trigger range is desired, preferably ranging between 1.4 to 15 and 2 g. Due to manufacturing tolerances and the displacement of the damping points of the leaf springs these specifications can be observed with very great effort only, however.